A 3D Kinematic Estimation of Knee Prosthesis from Fluoroscopic Images

Keywords

Abstract

We have developed two innovative techniques for
estimating 3D motion of the knee prosthesis from its 2D
perspective projections. One is a two-step estimation
algorithm and the other is a way to solve overlapping
problem. In our two-step estimation algorithm, the first
step estimation was done, in the same way as Banks and
Hodge's on the assumption of pseudo-orthogonal
projection. Then, the second step estimation was
succeeded based upon the perspective projection to
accomplish more accurate estimation. The other is an
estimation method to solve such a problem, as our
algorithm did not function when the silhouettes of tibio
and femoral components overlapped with each other.
Here first, interpolated the missing parts of silhouette
contour and then applied the clipping method. Simulation
results demonstrated that our two-step estimation
algorithm improved accuracies much, and also sufficient
accuracies could be assured even for the overlapped
silhouettes; equivalent to those without overlap. Finally,
we applied our algorithm to the fluoroscopic images. We
introduced not only the absolute positions/orientations for
each component but also the relative
positions/orientations between the both components.
Estimation results of the clinical applications
demonstrated that our algorithm worked well as like as
theoretical.